Bugfix in CDriver::PreprocessExtIter (FLOW-solver being called without asking whether it exists.)
Bugfix in CDriver::PreprocessExtIter (FLOW-solver being called without asking whether it exists.)

drewkett/SU2,srange/SU2,hlkline/SU2,drewkett/SU2,srange/SU2,drewkett/SU2,srange/SU2,srange/SU2,hlkline/SU2,hlkline/SU2,drewkett/SU2,drewkett/SU2,hlkline/SU2,hlkline/SU2